How to check if all objects in an array contains same keys and values?

Question

How to check if all objects in an array contains same keys and values

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:1, b: 2 }] // true

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:2, b: 1 }] //false

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2, c: 3}, {a:2, b: 1 }] //false

This is my trial that looks so ugly and bad and not working, i would be thankful if someone put an efficient code for that problem!

function test(arr){

   const firstItem = arr[0];
   const firstItemKeys = Object.keys(firstItem);

   for(let i = 0; i < firstItemKeys.length; i++) {
      for(let j = 0; j < arr.length; j++) {
         for(let x in arr[j]) {
             if(arr[j][x] !== firstItem[firstItemKeys[i]]) return false
         }
       }
   }

   return true
}

See https://stackoverflow.com/questions/201183/how-to-determine-equality-for-two-javascript-objects for ways to check if objects are equal. Then just use one of those techniques in the loop. — Barmar, Jun 18 '20 at 23:53
Some important restrictions for this question: Are outside libraries acceptable? Are the objects always a single level deep, or might they be nested? Can you confirm if values will always be scalar values? These will be important considerations for answering this to your requirements. — Alexander Nied, Jun 18 '20 at 23:55
@AlexanderNied no i don't want to use libraries, and no no nested objects and values not always scalar — Code Eagle, Jun 18 '20 at 23:59

score 3 · Accepted Answer · edited Jun 19 '20 at 13:14

3

Here is the code:

const arrOfObjects = [
  { a: 1, b: 2 },
  { a: 1, b: 2 },
  { b: 2, a: 1 },
]
function areEquals(a, b) {
  var keys1 = Object.keys(a)
  var keys2 = Object.keys(b)
  if(keys1.length !== keys2.length) {
    return false ;
  }
  for(key in a) {
    if(a[key] !== b[key])  return false;
  }
  return true ;
}
function checkArray(arr) {
  for (var i = 1; i < arr.length; i++) {
    if (!areEquals(arr[0], arr[i])) return false
  }
  return true
}
console.log(checkArray(arrOfObjects))

edited Jun 19 '20 at 13:14

Rahul Bhobe

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answered Jun 19 '20 at 00:04

Ehsan Nazeri

771
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If you switch the position of `a` and `b` in one object like `{ b: 2, a: 1 }` it'll return `false`. – Orilious Jun 19 '20 at 00:22
yes i was writing that comment the moment i saw yours @Armamedia – Code Eagle Jun 19 '20 at 00:24
@EhsanNazeri this will not work as OP as wanted if you have `[{a: 1, b: 2}, {a: 1, b: 2, c: 3}, {a:2, b: 1 }] like this. just FYI` – Always Helping Jun 19 '20 at 00:55

score 2 · Answer 2 · answered Jun 19 '20 at 00:00

2

If you can use lodash, then there is method _.isEqual

const _ = require('lodash')
const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:1, b: 2 }]
let isEqual = true
arrOfObjects.forEach(obj => {
  if (!_.isEqual(arrOfObjects[0], obj)) {
    isEqual = false
  } 
})

return isEqual

PS: This could be written in one line with reduce, but it will not be readable for anyone new to programming or javascript.

answered Jun 19 '20 at 00:00

libik

22,239
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Unfortunately the user indicated in the comments that outside libraries are not acceptable. – Alexander Nied Jun 19 '20 at 00:00
1

The OP said he does want to use libraries. So this will not help. – Always Helping Jun 19 '20 at 00:01

How to check if all objects in an array contains same keys and values?

2 Answers2

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